Hi, I'm looking to digitize my bluray and DVD library and I am looking to *avoid* using my main gaming rig. It uses too much power and heats up my apartment considerably, plus I would rather not leave that PC on for a month or two straight while I go through all 100-200 DVDs and Blurays. What's a low-voltage CPU or SoC solution that would work well with handbrake? Ideally it'd be relatively cheap, like <$500 for a chip, memory, mobo, and case/power supply (no hard drive or OS needed)

You can use a processor with QuickSync Video capability, but you should expect about 10% larger file sizes for the same quality as a software-based encode. There is an example of a benchmark for such a rig here. The encode-per-watt benchmark is hard to ignore, though.

If disk space is not a problem, you can go without encoding... Tools like MakeMKV do not use a lot of power to rip the video off the disks (it barely moves the CPU percentage on my machine when running 2 simultaneous rips), but you're "stuck" with full-size files. If the goal is just to get off the dependence on plastic media, that is THE place to start, and worry about encoding the MKV files to a smaller size over a few months.

200 blurays would take about 8-10TB of space "raw".

Edited to add: I forgot to mention - using QSV with handbrake requires Windows, so you'll also have to factor in the cost of a Windows license to go that route.

Disk space is a problem, Actually it's my plex server that's the problem. It cannot handle transcoding and adding subtitles to raw bluray files over the network, then transmitting the data over the network again to its destination. Whether it's a CPU, disk, or network bottleneck I don't know, but it causes all sorts of problems. I also only have 4TB to work with on my whole library, but that also includes files I need to share too, so the movie space is probably closer to 2.5TB.

The idea is to encode to 720p with decent quality, about 200-300MB per 24 minutes. I also want to de-grain older blurays with grainy footage to save space, and optimize some animated films and shows for file size.

Time is not an issue, I'm mainly trying to avoid excessive heat in my office (really makes it hard to work and the A/C already struggles to keep up during gaming sessions), and going above 1000Kwh per month (my electric company upcharges me if I do). It could take a year for all I care, as long as it gets done.

Some prioritization will probably be cheaper, long-term. If it's anime, do it first.... 70-90% space reduction is common, and frame rates during the encode are usually pretty good. If the NAS can have a USB drive plugged in, you might consider that for saving the rips to, then encode to the main NAS drive.

If speed isn't a big issue, an Atom processor can run handbrake without issue, is relatively low power, and will just churn away at the queue. Atoms are limited in the number of cores they have, but we're talking 15-30w instead of 70-150w. And, again, if you can tolerate the extra file size, the QSV hardware can get you double-digit frame rates at vastly lower power consumption.

Learning to use the command line and creating batch files works better for me than doing queues in the handbrake GUI.

OK, sounds promising. What would an i5-8250U or i5-7260U do in comparison to a modern Atom? There is a barebones kit I was looking at with those CPUs in it. They are both HT-enabled and have the same low power consumption, but I don't know if they're worth the price premium over a less popular Atom lineup.

I'm not a CPU geek, so I can't answer detailed questions. I do believe Intel considers the Atoms to be "end of life" products, though... We were told that when we went to re-order some boards we used for solar-powered web servers.

The power specs on the i5-8250U look pretty good, but figure it's going to run at the 25w mark during encodes. It would do better than the i5-7260U on encode speeds because of the increased core count.

25W is okay on the particular system, the system itself has will probably draw 40w with all other components at worst which won't heat up the room, much better than the 290w my gaming rig sucks up as a personal space heater.

I have an Intel Compute Stick STK2MV64CC (CS525) with the Intel® Core™ m5-6Y57 Processor 4M Cache, up to 2.80 GHz, which I believe is still the top option in a Compute Stick, and I believe the most powerful CPU per unit of power. It still takes about a day and a half to encode most modern BluRays at full 1080p. But a Compute Stick is awesome for taking your movies with you and plugging it into anything with a HDMI port. I have a SanDisk 400GB SD card, and their 256GB UltraFit USB in it, stuffed with our favorite movies. It’s awesome possum!